Various paint compositions are known to skilled artisans for painting automotive and architectural glass. Such paints are used, for example, to form opaque borders around the peripheral marginal surfaces of glazings used as windshields, sidelites, and backlites of motor vehicles.
Generally these compositions are ceramic compositions formed from a mixture of metal oxides in an organic vehicle. The mixture of metal oxides is adjusted so as to achieve a specific color for the ultimately produced fired ceramic paint. For example, the opaque peripheral marginal paint bands fired onto automotive glazings are generally black and may include oxides like chrome oxide, cobalt oxide and nickel oxide. The organic vehicles generally included in such compositions, e.g., pine oil, mineral oils, low molecular weight petroleum fractions and the like are used to allow the ceramic paint to be applied to the glass surface by brushing, spreading, or screen printing. The metal oxides are non-reactive with one another, as well as non-reactive with other materials like glass frits often contained in the ceramic paint. These glass frits are the materials which ultimately fuse the ceramic paint together, and to the glass sheet, to insure that the ceramic paint remains affixed to the glass sheet after being cooled to room temperature. When these materials are applied to a glass sheet, they are heated at high temperatures generally above the softening point of the glass to cure the paint and make the painted glass sheets suitable for further handling during a latter high temperature shaping process.
In view of environmental and commercial considerations, it would be desirable if water-based paints could be developed for use in place of such organic vehicle paints. It would be further desirable to develop a water-based paint which could be cured at relatively low temperatures rather than the high temperatures generally required for ceramic/organic vehicle paint curing. Subjecting the glass having the paint coating to such high temperatures during curing of the paint often impart undesirable optical distortions into the glass sheets. In order to be suitable as a replacement for the conventionally used ceramic paints, the water-based paint would need to provide a uniform coating, be durable, and also adhere well to the glass. One such water-based paint is disclosed in U.S. Pat. No. 5,518,535 entitled "Water-Based Paint For Glass Sheets" having the same inventorship as the present invention and being commonly assigned therewith.
It is an object of the present composition to provide a water-based paint composition which displays excellent adhesion to glass. It is a further object of this invention to provide a water-based paint which is curable at relatively low temperatures and which exhibits excellent durability. It is yet a further advantage of this invention to provide a water-based paint suitable for use on glass which may be exposed to a wide range of high temperatures (often 1250.degree. F. or more) generated during the tempering of the glass. Advantageously, the present invention water-based paint composition achieves these objectives.